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Morphologic Classification of Filtering Blebs after Glaucoma Filtration Surgery: The Indiana Bleb Appearance Grading Scale

Cantor, Louis B. MD; Mantravadi, Anand MD; WuDunn, Darrell MD, PhD; Swamynathan, Kala MD; Cortes, Arnold MD

Original Articles

Purpose To establish a new classification system for filtering blebs according to clinical morphologic parameters. The purpose of this classification system is to provide a uniform and objective assessment of bleb appearance and establish a framework system through which outcomes of filtration surgery may be better correlated to clinical morphology.

Materials and Methods The Indiana Bleb Appearance Grading Scale contains a set of photographic standards illustrating a range of filtering bleb morphology selected from the slide library of the Glaucoma Service at the Indiana University Department of Ophthalmology. These standards consist of slit lamp images for grading bleb height, extent, vascularity, and leakage with the Seidel test. For grading, the morphologic appearance of the filtration bleb is assessed relative to the standard images for the 4 parameters and scored accordingly. Fifty-one clinical bleb photographs were evaluated and scored by 3 glaucoma subspecialists in a masked fashion according to the scale.

Results For all of the grading scales, high interobserver agreement was found using the scale to classify the appearance of filtering blebs (height +0.76; extent +0.78; vascularity +0.90, interclass correlation coefficient for consistency using a 2-way mixed effect model).

Conclusion The Indiana Bleb Appearance Grading Scale is a simple, reproducible, yet comprehensive system for classifying the morphologic slit lamp appearance of filtration blebs.

Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana

Received November 13, 2002;

sent for revision January 15, 2003; accepted March 20, 2003.

Address correspondence and reprint requests to Louis B. Cantor, MD, 702 Rotary Circle, Indianapolis, IN 46202. E-mail:

© 2003 Lippincott Williams & Wilkins, Inc.